It is something we share with our closest genetic relatives, the chimpanzee.

Rational and Irrational Apes

Chimpanzees in the wild can demonstrate remarkable mental sophistication. I learned this directly in the summer of 1997, when I was living at a research station in the rainforest of western Uganda.

Harvard professor Richard Wrangham, who did some of his early work with Jane Goodall, founded the center in 1987. A central goal of the research was to follow and observe chimpanzees in their natural environment. When I arrived, the same group of chimpanzees (along with their offspring) had been observed and documented for 10 years.

In my stay with the chimpanzees, I grew to respect their intelligence. For example, one day I was following a group of wild chimpanzees when they entered an area of thick vegetation. My fellow human observers and I were unable to follow, and thus we lost contact with the animals.

Where could we find our chimpanzee group? My Ugandan companions suggested that we walk about two miles through the forest to a fig tree that was producing ripe fruit. Furthermore, the men suggested that we would arrive at the fig tree before the chimpanzees, and therefore we would be able to take a lunch break.

The Ugandans knew that the chimpanzees keep track of which trees are fruiting. Thus, the logical place to wait for them was at one of their tasty food sources. But how could we know when the chimpanzees would arrive? The answer is that the chimpanzees regulate their body temperature, and this provided an estimate for their arrival time.

When chimpanzees eat in these fig trees, they often climb high enough that they leave the shade of the forest floor and expose their dark and hairy coats to the sun. The chimpanzees dont like to overheat, so on sunny days, the chimpanzees tended to visit this particular tree in the cool

morning. On cloudy days, like the one in question, however, the chimpanzees tended to arrive later.

We marched off to the fruiting fig tree, ate our lunch, and had a nap. The chimpanzees arrived right on schedule! I found this amazing. To get to the right tree at the right time, the chimpanzees used a mental map of the forest, they understood the seasonality of the fruiting, they understood the weather, and they knew how to find their way. They did it perfectly!

So chimpanzees can be really, really smart. The Ugandan men were able to navigate their way through the forest only because of years of experience. If I had been alone, I would have died in the forest long before I found any food (or chimpanzees). So these chimpanzees were able to solve this navigation problem better than most humans.

In contrast to savvy chimpanzees in the wild, those in zoos and research centers often look less intelligent. I learned this lesson in a humorous way from my friend Brian Hare, whom I met in Uganda that summer when he was a college student. He subsequently earned his doctorate from Harvard, and is now an accomplished primatologist.

Brian did some of his early work with chimpanzees at the Yerkes Primate Center in Atlanta. As an enthusiastic young scholar, Brian decided to see if he could get the chimpanzees to imitate him. Although one often hears the expression monkey see, monkey do, there is very little evidence that monkeys or apes (chimpanzees are apes, not monkeys) learn through imitation.

Brians test of chimpanzee imitation took the following form. Each day, he planned to do a headstand in front of the chimpanzees. Since chimpanzees do not normally perform headstands, any such behavior would be clear evidence of imitation. Brian explained his idea to the workers who cared for the animals. Their experience with captive chimpanzees had made them a bit cynical, and they laughed at Brians youthful zest.

Undaunted, Brian proceeded to do a headstand in front of the captive

chimpanzees. What happened? Within a few moments, the chimpanzees did respond, not by doing headstands, but by throwing their dung at Brian. (Their aim was pretty good, and they seemed to especially enjoy hitting him in the face.) He quickly abandoned his headstand project.

Captive chimpanzees exhibit lots of strange behaviors that seem very different from the sophisticated rainforest navigation that I had observed in Uganda. In their artificial settings, captive chimpanzees have little to do (their food is provided), they do not travel long distances, and they even weigh much more than their wild counterparts.

In short, captive chimpanzees sit around, eat too much, exercise too little, and are so bored that they throw dung for entertainment. (Sound like your boss?)

Are chimpanzees supersmart, or are they overweight, lazy, and bored? The answer is that they are capable of both types of behavior; what they do depends on their environment. When chimpanzees are in their natural environment, their instincts guide them to appropriate behavior. In contrast, when chimpanzees are in certain types of unnatural environments, such as zoos and research centers, those same instincts get them in serious trouble.

Humans as Zoo Primates

Humans can be thought of as self-domesticated apes or as zoo primates. Our not too distant ancestors lived in small groups and earned their food the old-fashioned way-by hunting animals and gathering plants.

Technological change, first in the form of agriculture, and later in the industrial and information revolutions, has changed our world fundamentally. A modern city is as unnatural an environment for a human as a zoo is for a chimpanzee. (A big difference, of course, is that we have built and moved into our own zoos, while people placed other animals in zoos.)

In recent years, scholars have shown that some of our individual irrationality can be explained by understanding the differences between